The warning tag on a lawn mower states that it produces noise at level of 91.0dB. What is this in Wm^-2?

1 Answer
Oct 7, 2015

1,259mW//m^2

Explanation:

According to the equation for sound level

beta = 10 log (I/(I_0)),

where beta is sound level in decibels, I is intensity in W//m^2 and I_0 is the threshold intensity equal to the minimum that can be heard, which for humans is apparently 10^(-12)W//m^2.

Substituting in the given data and solving for the required unknown, we get :

91=10log(I/(10^(-12)))

#therefore 10^(9,1)=I/(10^-12)

thereforeI=10^((9,1-12)=)1,259mW//m^2